- Modern Dinocyst Key
- transparent cysts
- Septa and processes
- Processes distally connected
- Dalella chathamensis
Dalella chathamensis
Zonneveld, K.A.F. and Pospelova V. (2015). A determination key for modern dinoflagellate cysts. Palynology 39 (3), 387- 407.
single grain - reference collection Bremen
sample: GeoB 6423-1
eastern south Atlantic Ocean
photographs: Karin Zonneveld
Field characteristics
Dalella chathamensis McMinn et Sun 1994
Field characteristics:
Chrorate sperical to subspherical cysts with tabulation reflected by a trabeculum. Trabeculum is joined to autocyst at sulcus, archeopyle margin and the apex. Sulcal tabulation of the gonyaulacacean S-type. Archeopyle is precingular (paraplate ?3”).
Dimensions: Autocyst body diameter: 26–28 µm; diameter with trabeculum: 51–65 µm.
Motile affinity: unknown.
Stratigraphic range: late Pleistocene to Recent.
Comparison to other species:
This cyst is well recognisable at its trabeculum is only connected to the inner body at the sulcus. It most closely resembles Nematosphaeropsis labyrinthus, it differs however from this species by having a single trabeculae. In N. labyrinthus the processes are connected by parallel ribbon-like trabeculae.
D. chathamensis is abundant in the temperate to equatorial regions of the Southern Hemisphere north of the maximal extension of sea ice. In the northern Hemisphere it is restricted to the eastern Pacific Ocean and a few sites just north of the equator in the central Atlantic Ocean. Highest relative abundances are observed along the Antarctic sub-tropical and Antarctic Polar Fronts at the northern rim of the Antarctic Circumpolar Current. Although it is observed at a few coastal sites, it is mainly present in high abundances in the open oceans far away from the continental margins.
Environmental parameter range:
SST: -1.5 - 28.4°C (winter - summer), SSS: 32.1 - 36.9 (summer - autumn), [P]: 0.1 - 1.9 μmol/l, [N]: 0.04 - 25.8 μmol/l, chlorophyll-a: 0.1 - 3.1 ml/l, bottom water [O2]: < 6.1 ml/l.
D. chathamensis is restricted to cold/temperate to tropical regions with abundances > 5% where SST: are between 4.5 - 22.1°C (winter - summer). The SSS: range is small and it is absent in vicinity of river discharge plumes or other regions with reduced salinities. Cysts have been reported from oligotrophic to eutrophic environments. Bottom waters at few sites are anoxic/hypoxic but mostly bottom waters are well ventilated.
Comparison with other records:
This species is not reported from regions other than covered by this Atlas.